Should we all go nofollow?

Here's a thought. Wikipedia made all their external links nofollow. Many high authority sites only give nofollow, so we can link to them and give them our link juice which helps them stay up in the rankings but we can't get anything back.
If we all adopted the same policy and made all our external links nofollow the whole system would fail.
Why is it ok for some sites to be nofollow and not others?

It depends on the site format and Wiki being more of UGC (user generated content) it is better to be nofollow. Similarly most of the forums are also nofollow and I think it is better to be having it as nofollow if content is UGC.

I understand what you are saying, but here's an example. Yesterday I was on the Sitepoint forum, and there was a question about getting adwords coupons. I remembered your article on the subject and posted a link to it. But Sitepoint is also nofollow so you aren't getting any benefit from it. How can that be right?
I appreciate what you say about UGC but that's what moderators are for isn't it? Sitepoint could delete my link if they thought it inappropriate, but instead a genuinely placed link will go unrewarded (in the terms I am talking of).
In addition, this isn't limited to UGC sites.

Now that is the sad part of SEO with links because any site who can grab more dofollow links would rank higher and this is what over optimize sites is all about and so Google working on them to de-rank them. Luckily it is only blogs and article links from the content which are dofollow and other all links are more or less nofollow.

So guest posting and article directories are gaining lot of attraction these days.

This is how internet (read Google) works for great content.

Also I just checked your link and it was probably on v7n and not on sitepoint. Let me know if I am correct.

Sorry, my mistake, it was v7n which means it is dofollow
But if all links become nofollow (as I think you are suggesting) then even editorially given contextual links will count for nothing and the use of links as votes will cease. That's ok as long as whatever replaces it is up to the job of identifying great content. I don't see social media as being the alternative because it can be manipulated in just the same way. Is Google's artificial intelligence going to be able to do it by itself?

Artificial intelligence needs to be built in and so links for the sake of links does not mean much and so links from authority domains means lot more than links from link network blogs and so nofollow or dofollow would not matter too much in the near future.

Actually the concept of nofollow was to make sure all links don't pass the link juice but now it has become a way to link to others and so I think it needs some revelation but don't expect that anytime soon.

If Google stop considering websites value on do-follow backlinks and start giving value to them on content basis only, then almost all the spamming activities on the Internet for ranking factor will stop. In that case people will also have to admit the fact that links are for advertisements not for optimization …

If Google stop considering websites value on do-follow backlinks and start giving value to them on content basis only, then almost all the spamming activities on the Internet for ranking factor will stop. In that case people will also have to admit the fact that links are for advertisements not for optimization …

And start spamming their own pages at least.

On the other note Google is trying hard to get people to use Google +1 but it is not able to get it going to the extent it should.

On the other note Google is trying hard to get people to use Google +1 but it is not able to get it going to the extent it should.

People will only give much importance to Google +1 once all the websites go no-follow. Even though, Google also need to exclude backlink factor. So the expertise who thought they are able to manipulate Google search results by having bunch of do-follow links will at least focus on their content and will try to engage with their website's regular visitors or customers through various ways to receive more +1 …